Spring brake accumulator cylinder

ABSTRACT

For the assembly of a spring-type brake cylinder, a rear cylinder is provided with a preloaded spring, with a rear piston and with an intermediate flange. Then, a front cylinder, in which a front piston with an actuating rod for a brake element of the braking system is movably arranged, is fixed to the rear cylinder, so that the rear cylinder and the front cylinder are in contact with one another by means of a sliding rod passing through the intermediate flange. As a result, the front piston is displaceable by the rear piston.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a pneumatic actuator for the braking system ofa vehicle.

Pneumatic actuators of this type are often constructed as spring-typebrake cylinders comprising a rear cylinder in which a rear piston isdisplaceably arranged. One side of the rear piston and the inner wall ofthe rear cylinder form a rear ventilation chamber. A preloaded spring,which can be compressed by the rear piston, is provided on the otherside of the rear piston.

The rear ventilation chamber is sealed off by an intermediate flangetraversed by a sliding rod resting against the rear piston. The slidingrod can be displaced in the intermediate flange by the rear piston. Afront ventilation chamber delimited by a front piston movable in a frontcylinder is provided on the side of the intermediate flange situatedopposite the rear ventilation chamber. An actuating rod for a brakeelement of the braking system of the vehicle is provided on the frontside of the piston. The rear piston and the front piston are in contactwith one another by means of the sliding rod such that the front pistoncan be displaced by the rear piston.

When the vehicle is started, the rear ventilation chamber is filled withcompressed air against the pressure of the preloaded spring so that therear piston moves into the rear cylinder. The sliding rod also movestowards the rear in the intermediate flange and therefore no longer actson the front piston. The front piston and the actuating rod can,therefore, also move toward the rear into the front cylinder, therebyreleasing the brake element of the braking system. The vehicle thereforemoves from a state in which it is braked by the preloaded spring to anon-braked state. If compressed air is admitted to the front ventilationchamber, the front piston can be moved in the front cylinder, as aresult of which the brake element of the braking system can be actedupon by way of the actuating rod. Braking of the vehicle can thus beeffected in a selective manner.

In the event of the failure of the compressed-air supply of the vehicle,the pressure of the compressed air in the rear ventilation chamberdecreases. The preloaded spring then pushes the rear piston back intothe starting position, the sliding rod acting on the front piston. Thefront piston in turn displaces the actuating rod such that the brakeelement of the braking system is actuated.

The above-mentioned embodiment results in a fail-safe operation of thevehicle.

The pneumatic actuators known in the prior art have a complicated designand can only be produced with difficulty. Sealing problems furthermoreoften occur, particularly if the pistons used have flexible membranes.

It is therefore an aim of the invention to provide an improved pneumaticactuator which can be produced in a simple manner.

According to one of the ideas underlying the invention, the intermediateflange is received in the interior of the rear cylinder or in theinterior of the front cylinder. The front cylinder is fixed to the rearcylinder. This design results in considerable advantages over thepneumatic actuators known in the prior art. The actuator according tothe invention can first be designed to be stackable, e.g. in one step,the rear cylinder and the components therein and, in another step, thefront cylinder and the corresponding components. For the final assembly,the intermediate flange then simply has to be introduced into the rearcylinder or into the front cylinder, after which the connection betweenthe rear cylinder and the front cylinder is established.

A reliable connection between the rear cylinder and the front cylindercan be achieved by a form-locking connection, e.g. by means of athread-type connection or by means of a connection produced by a formingstep. In particular, it is contemplated for one wall of the frontcylinder and one wall of the rear cylinder to be mutually connected bymeans of a curled region. A shoulder is advantageously provided in oneof the walls of the front cylinder or the rear cylinder, over which aregion of the other cylinder is curled. Particularly durable connectionsbetween the rear cylinder and the front cylinder can be produced in thismanner, and a reliable connection can be established over the entirecircumference of the housing of the relevant cylinder.

One particularly advantageous embodiment of the invention is produced ifthe front piston or the rear piston has a substantially circulardisc-shaped or ring-shaped flexible membrane connected in the region ofits outer edge to the wall of the front cylinder or of the rearcylinder. In this embodiment of the relevant piston, the membrane edgeis enclosed between the wall of the cylinder and the intermediateflange. A connection of this kind can be produced in a particularlysimple and reliable manner by means of the pneumatic actuator accordingto the invention. Unlike the pneumatic actuators known in the prior art,the pneumatic actuator according to the invention can be finished andsealed in a simple manner in one step. By virtue of the fact that thewall of the rear cylinder is joined to the wall of the front cylinder,any membrane provided can be installed in a simple and particularlyreliable manner, with particularly good sealing being achieved.

The production method according to the invention provides that the frontcylinder is connected to the rear cylinder in a final step, wherein thefront cylinder can be fixed to the rear cylinder by welding, screwing,soldering, curling and/or clamping with a sleeve.

The invention will be described in more detail by way of threeembodiments illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a first spring-type brake cylinder;

FIG. 2 is a cross-sectional view of a second spring-type brake cylinder;and

FIG. 3 is a cross-sectional view of a third spring-type brake cylinder.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-section through a first spring-type brakecylinder 1. The spring-type brake cylinder 1 has a pot-shaped rearcylinder 2 made of sheet steel. A rear piston 3 is provided in the rearcylinder 2 and is sealed off from the inner wall of the rear cylinder 2by means of a circumferential seal 4. The rear piston 3 is arranged in alongitudinally displaceable manner in the rear cylinder 2. A preloadedspring 5 is provided on the rear face of the rear piston 3 and issupported in a bottom region 6 of the rear cylinder 2.

The wall of the rear cylinder 2 expands toward a receiving region 7relative to the bottom region 6.

A circular-disc-shaped intermediate flange 8 is received in thereceiving region 7 and is sealed off in an airtight manner from thereceiving region 7 on its outer face by means of an O-ring 9. Theintermediate flange 8 is provided in the region of its axis of symmetrywith a through opening 10 in which a sliding rod 11 formed on the rearpiston 3 is guided. A rubber seal 12 is introduced between the slidingrod 11 and the through opening 10 for sealing.

A ventilation hole 13 is also provided on one side in the intermediateflange 8, in the form of a radial bore in the outer edge of theintermediate flange 8. At the outlet point of the ventilation hole 13, arecess 14 is provided in the area of the receiving region 7 for theconnection of a supply line. A rear ventilation chamber 15 formed by theintermediate flange 8, the rear cylinder 2 and the rear piston 3 can besupplied with compressed air by means of the ventilation hole 13, sothat the rear piston 3 can be moved into the position shown in FIG. 1against the compressive force of the preloaded spring 5.

The front cylinder 20, which is pot-shaped and made of sheet steel,adjoins the rear cylinder 2. The front cylinder 20 has a beaded fixingedge 21, which projects over the outer face of the front cylinder 20 ina shoulder-like manner. The receiving region 7 is bent over by a curlingprocess in such a manner that the fixing edge 21 is axially secured. Acircular-disc-shaped flexible rubber membrane 22, which delimits a frontventilation chamber 23 is provided between the fixing edge 21 and theintermediate flange 8. The front ventilation chamber 23 is moreover alsoformed by one side of the intermediate flange 8 and a region of thesliding rod 11 projecting through the intermediate flange 8.

Compressed air can be admitted selectively to the front ventilationchamber 23 by means of ventilation devices not visible in this view.

A pressure plate 24 with an actuating rod 25 extending in the region ofthe axis of symmetry of the first spring-type brake cylinder 1 isprovided in the inner region of the rubber membrane 22. The pressureplate 24 is pressed continuously against the rubber membrane 22 by areturn spring 26. A centering opening 27 provided in the pressure plate24 receives a centering nipple 28 formed in the rubber membrane 22 sothat the position of the actuating rod 25 remains within a desiredregion during the movement of the pressure plate 24 and the rubbermembrane 22.

Expanding bellows 29 extending from an outlet opening 30 in the bottomof the front cylinder 20 to the actuating rod 25 seal off the interiorof the front cylinder from dirt entering from the outside. Furthermore,two fixing bolts 31 are inserted into the bottom of the front cylinder20 in order to fix the first spring-loaded brake cylinder 1 to avehicle.

Particularly good sealing of the front ventilation chamber 23 isprovided in the case of the first spring-type brake cylinder 1. Theouter edge of the rubber membrane 22 specifically is particularlyreliable and tight as a result of this design of the rear cylinder 2, ofthe intermediate flange 8, of the fixing edge 21 and of the edge of themembrane 22, which has a wedge-shaped cross-section in the fixingregion.

The spring-type brake cylinder 1 is actuated in a known manner withcompressed air being admitted to the rear ventilation chamber 15 or tothe front ventilation chamber 23. A brake element (not shown in thisview) of a vehicle is actuated by means of the actuating rod 25.

The first spring-type brake cylinder 1 is assembled as follows. The rearcylinder 2 is prepared in a first production step. After that, thepreloaded spring 5 is inserted into the rear cylinder 2 together withthe rear piston 3. The intermediate flange 8 is then inserted into therear cylinder 2 so that it is situated in the receiving region 7. Therubber membrane 22 is then placed on the intermediate flange 8, so thatits outer edge rests against the inner wall of the rear cylinder in thereceiving region 7. The pressure plate 24 is then placed on the rubbermembrane 22 together with the return spring 26, the front cylinder 20finally being pressed into the receiving region 7 of the rear cylinder 2with a constant compressive force against the pressure of the returnspring 26 until it rests on the outer edge of the rubber membrane 22. Inthis state, the edge of the receiving region 7 projecting over the frontcylinder 20 is curled so as to produce the connection between the frontcylinder 20 and the rear cylinder 2 shown in FIG. 2. The edge region ofthe rubber membrane 22 is compressed in the longitudinal direction ofthe first spring-type brake cylinder 1 so as to produce a tightconnection.

FIG. 2 is a cross-sectional view of a second spring-type brake cylinder35. The second spring-type brake cylinder 35 is comprised of a rearcylinder 36, which is pot-shaped and made of sheet steel, and a frontcylinder 20′ which, together with the components received therein,corresponds essentially to the front cylinder of FIG. 1. The fixing edge21′ of the front cylinder 20′ has a larger diameter than thecorresponding fixing edge 21 of the front cylinder 20 of FIG. 1. Therear cylinder 36 expands toward a receiving region 38 with the formationof a shoulder 37. A preloaded spring 39, which can be preloaded relativeto a preloaded spring pressure plate 40 is provided on the bottom of therear cylinder 36. A mechanical return device (not shown here) foractuating the preloaded spring pressure plate 40, by means of which thepreloaded spring 39 can be compressed into the position shown in FIG. 2,is also provided.

Furthermore, an accumulator membrane 41 made of flexible material isprovided in the rear cylinder 36. The accumulator membrane 41 rests bymeans of its outer edge with a wedge-shaped cross-section against theshoulder 37 in the receiving region 38. At its inner region, theaccumulator membrane 41 engages by means of a centering cam 42 in acentering opening 43 of the preloaded spring pressure plate 40. Anaccumulator membrane return spring 44 presses the accumulator membrane41 against the preloaded spring pressure plate 40 by means of anaccumulator membrane plate 45. A sliding rod 46 extending in thedirection of the axis of symmetry of the rear cylinder 36 is provided ina central region of the accumulator membrane plate 45. The sliding rod46 is guided in an airtight region of an intermediate flange insert 47which is inserted into a central opening of an intermediate flange 48.The intermediate flange 48 is in turn inserted into the receiving region38 of the rear cylinder 36. The intermediate flange 48 clamps theaccumulator membrane 41 against the shoulder 37.

Together with the accumulator membrane 41, the intermediate flange 48forms a rear ventilation chamber 49 to which compressed air can beadmitted by means of a rear ventilation hole 50 in an edge region of theintermediate flange 48 and by means of a rear recess 51 in the receivingregion 38. On the sliding rod of the intermediate flange 48, togetherwith the rubber membrane 22 in the front cylinder 20′, the intermediateflange 48 forms the front ventilation chamber 23′ to which compressedair can be admitted by means of a front ventilation hole 52 in theintermediate flange 48 and a front recess 53 in the receiving region 38.

The method of operation of the second spring-type brake cylinder 35corresponds essentially to that of the spring-type brake cylinders knownfrom the prior art. The preloaded spring 39 can be moved into theposition shown in FIG. 2 by pressurizing the rear ventilation chamber49. By admitting compressed air to the front ventilation chamber 23′,the actuating rod 25 can be made to move a brake element (not shown inthis view) of a braking system of a vehicle.

The second spring-type brake cylinder 35 is assembled as follows. Therear cylinder 36 is first prepared, specifically with the preloadedspring 39 and the preloaded spring pressure plate 40 inserted.Subsequently, the accumulator membrane 41 is inserted into the receivingregion 38 so that its edge region is situated on the shoulder 37. Theaccumulator membrane plate 45, the sliding rod 46 and the intermediateflange 48 with the intermediate flange insert 47 are then inserted intothe receiving region 38. The front cylinder 20′ and the componentscontained therein, including the rubber membrane 22, are then insertedinto the receiving region 38, the entire second spring-type brakecylinder 35 being compressed along its axis of symmetry by means of atensioning device not shown in FIG. 2. The fixing edge 21′ is thenpressed against the shoulder 37 of the receiving region 38, withclamping of the rubber membrane 22, the intermediate flange 48 and theaccumulator membrane 41. In a final step, the edge of the receivingregion 38 projecting over the fixing edge 21′ is curled into theposition shown in FIG. 2, so that the front cylinder 20′ and the rearcylinder 36 are firmly connected with one another.

FIG. 3 is a cross-sectional view of the third spring-type brake cylinder60. The third spring-type brake cylinder 60 is comprised of a rearcylinder 61, which is pot-shaped and made of sheet steel, and a frontcylinder 20″ which, together with the components contained therein,corresponds essentially to the front cylinder 20 of FIG. 1.

A preloaded spring 62, together with a preloaded spring pressure plate63, is provided in the bottom region of the rear cylinder 61. An insertring 64 is also inserted into the rear cylinder 61 and rests against theinner wall of the rear cylinder 61. An accumulator membrane 65 extendsacross the rear cylinder 61 from the end of the insert ring 64 situatedopposite the bottom of the rear cylinder 61. The edge of the accumulatormembrane 65 has a wedge-shaped cross-section situated on the edge of theinsert ring 64, provided at this point with an inclination from theinside to the outside relative to the wall of the rear cylinder 61. Theaccumulator membrane 65 is provided on its inner face with a centeringcam 66 which engages in a centering opening 67 in the preloaded springpressure plate 63.

An intermediate flange 68 provided on its side directed towards theaccumulator membrane 65 with a region sloping downwards toward theoutside relative to the wall of the rear cylinder 61 is furthermoreinserted into the rear cylinder 61. This region is situated on the edgeregion of the accumulator membrane 65. The intermediate flange 68 isprovided in its center with an intermediate flange insert 69, in which asliding rod 70 is movably guided. The sliding rod 70 is provided on itsside directed toward the bottom of the rear cylinder 61 with anaccumulator membrane plate 71. An accumulator membrane return spring 72extends between the accumulator membrane plate 71 and the intermediateflange 68. A rear ventilation chamber 73, to which compressed air can beadmitted by means of ventilation devices not shown in this view, isformed between the accumulator membrane 65 and the intermediate flange68.

A circumferential ring-shaped rubber membrane groove 74 is formed in theintermediate flange 68 in a region situated close to the inner wall ofthe rear cylinder 61 on the side opposite the rear ventilation chamber73. A thickened outer edge region 75 of the rubber membrane 22″ isinserted into the rubber membrane groove 74. The outer edge region 75 ispressed into the intermediate flange 68 by a fixing edge 21″ of thefront cylinder 20″. The front ventilation chamber 23″, to whichcompressed air can be admitted by means of ventilation devices not shownin this view, is formed between the rubber membrane 22″ and theintermediate flange 68. A front pressure plate 24″ connected to anactuating rod 25″ projecting from the front cylinder 20″ rests againstthe rubber membrane 22″.

The third spring-type brake cylinder 60 operates in essentially the samemanner as the spring-type brake cylinders known in the prior art, i.e.,by admitting compressed air to the rear ventilation chamber 73 and tothe front ventilation chamber 23″. A brake element (not shown in thisview) of a braking system of a vehicle can be actuated by the movableactuating rod 25″.

The third spring-type brake cylinder 60 is assembled as follows.

The rear cylinder 61 is prepared in a first production step. Thepreloaded spring 62, the insert ring 64, the preloaded spring pressureplate 63 and the accumulator membrane 65 are inserted one after theother into the rear cylinder 61. Subsequently, the accumulator membraneplate 71, the accumulator membrane return spring 72 and the intermediateflange 68, together with the intermediate flange insert 69 and thesliding rod 70, are inserted until they are situated in the positionshown in FIG. 3. Then, the rubber membrane 22″ is inserted in such amanner that its outer edge region 75 is situated in the rubber membranegroove 74. Finally, the front cylinder 20″ is inserted into the rearcylinder 61. The third spring-type brake cylinder 60 is compressed onthe whole in its longitudinal direction by means of a tensioning devicenot shown in this view, so that the rubber membrane 22″ is pressedfirmly into the rubber membrane groove 74 by means of its outer edgeregion 75. Moreover, the outer edge region of the accumulator membrane65 is compressed between the intermediate flange 68 and the insert ring64. In this state, the projecting edge of the rear cylinder 61 is curledaround the fixing edge 21″ of the front cylinder 20″ in such a mannerthat a firm connection is established between the front cylinder 20″ andthe rear cylinder 61.

In other embodiments not shown here, the arrangement of the frontcylinder and the rear cylinder is reversed, so that essentially all ofthe components are first inserted into the front cylinder. Finally, therear cylinder is then fitted to the front cylinder, after which aconnection is established between the front cylinder and the rearcylinder. The connection between the front cylinder and the rearcylinder can also be accomplished, in particular, by means of athread-type connection, by means of a clamping bar or by means of aclamping sleeve. The front cylinder and the rear cylinder can also bemutually connected according to the invention by electric welding.

1-8. (canceled)
 9. Pneumatic actuator for a braking system of a vehicle,comprising: a rear cylinder in which a rear piston is displaceablyarranged, one side of the rear piston and an inner wall of the rearcylinder forming a rear ventilation chamber; a preloaded spring providedon the other side of the rear piston; a front cylinder in which a frontpiston having a rubber membrane is movably arranged, a rear side of thefront piston forming part of a front ventilation chamber; an actuatingrod for a brake element of the braking system provided on a front sideof the front piston; a sliding rod by way of which the rear piston andthe front piston are in mutual contact such that the front piston isdisplaceable by the rear piston; an intermediate flange provided in aregion between the front cylinder and the rear cylinder, theintermediate flange being penetrated by the sliding rod; wherein theintermediate flange is either received only in an interior of the rearcylinder or in an interior of the front cylinder in an expandedreceiving region; and wherein the front cylinder and the rear cylinderare form-lockingly connected with one another, an outer membrane edge ofthe rubber membrane on one side resting on the intermediate flange andon the other side resting on the connection of the front and rearcylinder.
 10. Pneumatic actuator according to claim 9, wherein a wall ofthe front cylinder and a wall of the rear cylinder are mutuallyconnected via a curled region of one wall with a shoulder of the otherwall.
 11. Pneumatic actuator according to claim 9, wherein the rubbermembrane of the front piston has an essentially circular-disc-shaped orcircular-ring-shaped flexible construction, and is connected in theregion of its outer membrane edge with the wall of the front cylinder,the outer membrane edge being enclosed between the wall of the frontcylinder and the intermediate flange.
 12. Pneumatic actuator accordingto claim 10, wherein the rubber membrane of the front piston has anessentially circular-disc-shaped or circular-ring-shaped flexibleconstruction, and is connected in the region of its outer membrane edgewith the wall of the front cylinder, the outer membrane edge beingenclosed between the wall of the front cylinder and the intermediateflange.
 13. Pneumatic actuator according to claim 9, wherein the rearpiston has an essentially circular-disc-shaped or circular-ring-shapedflexible membrane, which is connected in a region of its outer membraneedge with the wall of the rear cylinder, the outer membrane edge beingenclosed between the wall of the rear cylinder and the intermediateflange.
 14. Pneumatic actuator according to claim 10, wherein the rearpiston has an essentially circular-disc-shaped or circular-ring-shapedflexible membrane, which is connected in a region of its outer membraneedge with the wall of the rear cylinder, the outer membrane edge beingenclosed between the wall of the rear cylinder and the intermediateflange.
 15. Pneumatic actuator according to claim 11, wherein the rearpiston has an essentially circular-disc-shaped or circular-ring-shapedflexible membrane, which is connected in a region of its outer membraneedge with the wall of the rear cylinder, the outer membrane edge beingenclosed between the wall of the rear cylinder and the intermediateflange.
 16. Pneumatic actuator according to claim 12, wherein the rearpiston has an essentially circular-disc-shaped or circular-ring-shapedflexible membrane, which is connected in a region of its outer membraneedge with the wall of the rear cylinder, the outer membrane edge beingenclosed between the wall of the rear cylinder and the intermediateflange.
 17. Pneumatic actuator according to claim 9, wherein theactuator is a spring-type brake cylinder.
 18. Pneumatic actuatoraccording to claim 16, wherein the actuator is a spring-type brakecylinder.
 19. Method of assembling a pneumatic actuator for a brakingsystem of a vehicle, the method comprising the acts of: a) providing arear cylinder; b) introducing a preloaded spring into the rear cylinder;c) introducing a rear piston into the rear cylinder; d) introducing anintermediate flange into the rear cylinder; e) fixing a front cylinder,in which a front piston with an actuating rod for a brake element of thebraking system is movably arranged, to the rear cylinder while enclosingan edge of a flexible membrane of the front piston, so that the rearcylinder and the front cylinder are in contact with one another via asliding rod passing through the intermediate flange, the front pistonbeing displaceable by the rear piston; and performing the fixing act e)after acts a) to d).
 20. Method according to claim 19, wherein thefixing operation in act e) is carried out by at least one of welding,screwing, curling, and clamping with a sleeve.
 21. Method of assemblinga pneumatic actuator for a braking system of a vehicle, the methodcomprising the acts of: a) providing a rear cylinder; b) introducing apreloaded spring into the rear cylinder; c) introducing a rear pistoninto the rear cylinder; d) providing a front cylinder in which a frontpiston with an actuating rod for a brake element of the braking systemis movably arranged; e) introducing an intermediate flange in the frontcylinder; f) fixing a front cylinder to the rear cylinder, whileenclosing an edge of a flexible membrane of the front piston, so thatthe rear cylinder and the front cylinder are in contact with one anothervia a sliding rod passing through the intermediate flange, the frontpiston being displaceable by the rear piston; and performing the fixingact f) after acts a) to d).
 22. Method according to claim 21, whereinthe fixing operation in act f) is carried out by at least one ofwelding, screwing, curling, and clamping with a sleeve.